Molecular cloning of a Bacteroides caccae TonB-linked outer membrane protein identified by an inflammatory bowel disease marker antibody.

Commensal enteric bacteria are a required pathogenic factor in inflammatory bowel disease (IBD), but the identity of the pertinent bacterial species is unresolved. Using an IBD-associated pANCA monoclonal antibody, a 100-kDa protein was recently characterized from an IBD clinical isolate of Bacteroides caccae (p2Lc3). In this study, consensus oligonucleotides were designed from 100-kDa peptides and used to identify a single-copy gene from the p2Lc3 genome. Sequence analysis of the genomic clone revealed a 2,844-bp (948 amino acid) open reading frame encoding features typical of the TonB-linked outer membrane protein family. This gene, termed ompW, was detected by Southern analysis only in B. caccae and was absent in other species of Bacteroides and gram-negative coliforms. The closest homologues of OmpW included the outer membrane proteins SusC of Bacteroides thetaiotaomicron and RagA of Porphyromonas gingivalis. Recombinant OmpW protein was immunoreactive with the monoclonal antibody, and serum anti-OmpW immunoglobulin A levels were elevated in a Crohn's disease patient subset. These findings suggest that OmpW may be a target of the IBD-associated immune response and reveal its structural relationship to a bacterial virulence factor of P. gingivalis and periodontal disease.

The Crohn's disease-associated bacterial protein I2 is a novel enteric t cell superantigen.

An aberrant T cell response to enteric bacteria is important in inflammatory bowel disease. However, the identity of relevant microbial antigens is unknown. Here, we report the presence of I2, a Crohn's disease-associated microbial gene, in the murine intestine. The I2 protein induced a proliferative and IL-10 response by CD4(+) T cells from unimmunized mice. The I2 response was dependent on MHC class II-mediated recognition but did not require antigen processing. Selective activation was observed for the TCR-Vbeta5 subpopulation. These findings indicate that the I2 protein is a new class of T cell superantigen and suggest that colonization by the I2 microorganism in susceptible hosts may provide a superantigenic stimulus pertinent to Crohn's disease pathogenesis.

Identification of a novel bacterial sequence associated with Crohn's disease.

BACKGROUND & AIMS: Enteric microorganisms are implicated in the pathogenesis of Crohn's disease (CD), but no clear bacterial or viral species has been identified. In this study, representational difference analysis (RDA) was used to isolate DNA segments preferentially abundant in lamina propria mononuclear cells of lesional mucosa vs. adjacent uninvolved mucosa. METHODS: Two RDA-derived microbial sequences were isolated (I1 and I2) and identified as novel homologues of the ptxR and tetR bacterial transcription-factor families. RESULTS: Quantitative competitive polymerase chain reaction of paraffin-embedded intestinal specimens from 212 patients showed that I2 DNA was present in many CD colonic lesions (43%), but was infrequent in other colonic specimens (9% of ulcerative colitis lesions and 5% of non-inflammatory bowel disease diseases; P<0.0001). I2 was prevalent in ileal specimens, regardless of disease status (43%-54%). Enzyme-linked immunosorbent assay analysis of 150 individuals with an I2 glutathione-S-transferase fusion protein showed frequent immunoglobulin A seroreactivity in CD (54% of patients), but infrequent seroreactivity in patients with ulcerative colitis, other inflammatory enteric diseases, or normals (10%, 19%, and 4%, respectively; P<0.001 to 0.00001). CONCLUSIONS: These findings relate CD to a novel lesion-localized and immunologically associated bacterial sequence, suggesting that the microorganism expressing the I2 gene product may be related to CD pathogenesis.

Defining new pathogens and nonculturable infectious agents associated with inflammatory bowel disease.

The causes of inflammatory bowel disease remain uncertain, but increasing evidence supports roles for two pathogenic processes: genetic susceptibility in the host and an aberrant host response to enteric bacteria. Here, we review studies showing that the pathogenesis of inflammatory bowel disease involves both bacterial agents and genetic susceptibilities. We discuss the roles of known and novel commensal intestinal bacteria in the pathogenesis of inflammatory bowel disease and the various recombinant approaches used to identify these pathogens.

Chromosome 22q11.2 interstitial deletions among childhood-onset schizophrenics and "multidimensionally impaired".

Since its first description almost a century ago schizophrenia with childhood onset, a rare yet devastating disorder, has been diagnosed in children as young as age 5. Recently, the velocardiofacial syndrome, whose underlying cause is interstitial deletions of 22q11.2, was found in 2 of 100 cases of schizophrenics with adult onset [Karayiorgou et al., Proc Natl Acad Sci USA 92: 7612-7616, 1995]. No study has documented the prevalence of velocardiofacial syndrome and the 22q11.2 deletion in a population of schizophrenics with childhood onset. Here we describe the result of such a study in a sample originally selected for a trial of atypical antipsychotic drugs. A separate group of patients was also included in the study; they can best be accounted for as a variant of childhood-onset schizophrenia (COS) and had been provisionally termed "multidimensionally impaired." Fluorescent in situ hybridization screening of 32 COS and 21 multidimensionally impaired patients revealed 1 COS patient with an interstitial deletion spanning at least 2.5 megabases.